Membrane type storage tank



April 16, 1963 c. D. DOSKER MEMBRANE TYPE STORAGE TANK 2 Sheets-Sheet 1Filed Dec. 19, 1960 INVENTOR. Carnelzus D. Dos/(er April 16, 1963 c. D.DOSKER 3,085,708

MEMBRANE TYPE STORAGE TANK Filed Dec. 19, 1960 2 Sheets-Sheet 2INVENTOR. Cornelzus D, Dos/(er This invention relates to a storagefacility designed for use with liquids or fluids having a temperaturedifiering widely from the ambient temperature and it relates moreparticularly to a tank of large capacity for the storage andtransportation of a low boiling liquefied gas, such as liquefied naturalgas.

In my Patent No. 2,954,892, issued October 4, 1960, entitled Vessel forStoring Cold Liquids, description is made of a facility for the landstorage of large volumes of cold liquefied gas. The liquid is adapted tobe confined within an enclosure formed of a continuous lining formed ofa thin film of fluid and vapor impervious material, hereinafter referredto as a membrane, which is incapable of self-sufficiency under load butwhich is forced by the load of the liquid in storage against theinsulation layer for support.

A membrane type tank of the type described offers considerable advantageover the construction of conventional tankage for housing large volumesof extremely cold liquid. It does away with the high cost of aself-sufficient tank housed within an insulated space. For example, inthe manufacture of a self-sufficient tank of aluminum plate, orstainless steel, high nickel steel, or other metal capable of retainingstrength and ductility at the cold temperatures of the liquid (-240" F.to -258 F. for natural gas, depending upon the amount of higher boilinghydrocarbons in the natural gas), the cost of self-sufficient tanks forhousing as much as 30,000 barrels is in the order of hundreds ofthousands of dollars. Further, such selfsufiicient tanks cannot berigidly tied into the insulated structure for support because of thenecessity to permit relative movements between the tank and thesupporting structure due to the differences in expansion and contractionin response to the great differences in temperature change since thetank will be subject to a temperature change of from 80 F., when empty,to about 25(} F. when filled, whereas the supporting structure will haveto be insulated from the tank so that it will remain at about ambienttemperature. In a tank of 100 feet by 100* feet by 60 feet, the changein dimension in the tank may range from 6 to 10 inches in the variousdirections.

In a membrane type tank, it is sufiicient to make use of a thin film ofa fiuid and vapor impervious material formed as a lining about the innersurface of an insulated space which is characterized by structuralstrength and dimensional stability to maintain the liquid load when thelining is forced into engagement with the insulated surface for support.Under such circumstances, the lining merely functions as a liquid andfluid impervious barrier to confine the liquid within the insulatedspace but it contributes little by way of structural strength or supportof the liquid load. Thus the lining or membrane can be fabricated at lowcost of a minimum amount of material, representing a many-fold savingsover and above the self-contained storage tanks.

The construction of a membrane type tank is faced by a number ofproblems which are not present in a self-sulficient tank. Because of thelack of self-sufficiency, it is desirable to provide means forsupporting the membrane as a lining about the insulated space in amanner to prevent collapse when the liquid is removed. Another problemwhich is also faced by a self-suificient tank, but in a different way,is the need to permit freedom of the film or membrane for expansion andcontraction movements 3,085,708 Patented Apr. 16, 1963 relative to thesupporting insulation layer due to temperature change but while stillmaintaining proper stabilization of the lining.

In my aforementioned patent, the membrane is formed of interconnectedsegments which are individually supported from the insulation at spacedapart points with corrugations extending lengthwise and crosswise ineach of the segment to make additional amounts of material availablethroughout the entire area of the lining for expansion and contractionwithout substantial change in dimension. The joinder of the individualsegments into a continuous fluid and vapor impervious lining and thesupport thereof can be achieved but with great difficulty and atconsiderable expense.

It is an object of this invention to produce and to provide a method forproducing a membrane type tank for the storage and/or transportation ofan extremely cold liquid and it is a related object to produce and toprovide a method for producing a tank of the type described which isformed of relatively low cost and readily available materials; which canbe mounted in position of use to form a continuous fluid and vaporimpervious lining at minimum expense; which embodies a simple andefiicient means to prevent collapse; which embodies a simple andinexpensive means for support in a manner which permits freedom ofmovement relative to the housing in expansion and contraction due totemperature change, and which is simple in construction and easy inoperation to provide a sturdy storage facility of large capacity.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings in which:

FIG. 1 is a schematic sectional elevational view of a storage tankembodying the features of this invention;

FIG. 2 is a sectional view taken substantially along the line 22 of FIG.1, and

FIG. 3 is a sectional elevational view similar to that of FIG. 1 butshowing a further modification in the construction thereof.

The invention will be described with reference to the storage ofliquefied natural gas in large volume. Under such conditions, it ispractical only to store the liquid at atmospheric pressure or slightlyabove. At atmospheric pressure, the liquefied gas will be at atemperature of about 240 F. to 258 F. depending upon the amount ofheavier hydrocarbons present since liquefied methane, the majorcomponent of natural gas, has a boiling point of 258 F. at atmosphericpressure. It will be understood that the concepts of this invention willhave application also to the storage of other cold fluids and liquefiedgases.

In accordance with the practice of this invention, there is provided astructurally strong and dimensionally stable housing 10, illustrated asa rectangular housing having vertically disposed side walls 12, frontand back walls '14, a bottom wall -16 and a top wall 18. For purposes ofilustr-ation, the walls are shown as being constructed of a thermalinsulating material 22 to define an insulated storage space 20therebetween but it will be understood that the housing can beconstructed of an outer shell or frame of a structurally Strongmaterial, such as metal plate, with or without reinforcement, with athick layer of insulating material separating the metal frame from theinsulated storage space 20.

The insulation layer 22 constituting the entire structure of the housingor a part thereof is preferably fabricated of a structurally strong anddimensionally stable insulating material, such as panels or plies of aporous wood like balsa wood, quippo, etc., or of rigid foams of plastic,glass or cement, either in the form of panels or foamed in placeinsulation, or of panels of honeycomb with the cells extendinghorizontally endwise between the inner and outer surfaces. The inventiveconcept can best be illustrated with reference to a housing ofrectangular shape but it will be apparent from the description thattanks of other shapes in horizontal cross-section, but preferably withflat walls, can be employed.

Supported within the insulated space 20 and adjacent the inner surfacesof the insulation layers is a lining 26 of a fluid and vapor imperviousmaterial which completely covers the inner surfaces of the vertical andbottom walls of the housing to a height greater than the level of liquidadapted to be housed within the tank. An important concept of thisinvention resides in the construction and in the mounting of the liningformed of the thin membrane-like material.

The portions of the lining covering the front, back and bottom walls (orthe side and bottom walls if the former are of substantial width) areformed of continuous strips 28 of the fluid and vapor impervious sheetstock dimensioned to have a length which corresponds to the width of thebottom wall 16 plus the height to which the lining is adapted to coverthe front and back walls plus an additional amount for expansion andcontraction. The strips 28 are arranged in side-by-side relation withthe adjacent edges 30 being joined one to another in sealing relation,as by welding, to define the continuous front, bottom and back wallportions 32, 34 and 36 respectively of the membrane container. Thus thetwo opposite walls 14 of greatest dimension and the bottom wall 16 arelined with membranes which extend continuously downwardly along onewall, across the bottom wall and upwardly along the opposite wall. Itwill be apparent that the strips can be joined one to the other insealing relationship while within the housing or separate and aparttherefrom where joinder, as by welding, can be more easily andeffectively carried out to preform the lining covering the three largewalls of the insulated space. Similarly, the linings for the side walls12 are formed of continuous strips dimensioned to have a lengthcorresponding to the height to which the lining rises in the tank, plusthe additional amount for expansion, and arranged in side-by-siderelation for joinder of the adjacent edges in sealing relation toprovide a continuous cover 38 over the side walls of the insulatedspace. The adjacent lateral edges of the panels 38, 32 and '36 arejoined one to the other in sealing relation and the bottom edges of thepanels 38 are joined to the lateral edges of the panel section 34 todefine a fluid and vapor impervious enclosure therebetween.

In this construction, the only welds that are required to be made arealong the seams 40 between the lateral edges of the adjacent strips oflining material, most, if not all, of which can be preformed outside ofthe tank Where access can be made to all such surfaces more easily andelfectively to join the edges in sealing relation. In the event that thepanels 38 for the side walls are preformed separate and apart from thepanels covering the front, back and bottom walls, joinder can beeffected while in position of use merely by joining the lateral edges ofthe lining covering the three side and bottom walls with the adjacentlateral edges and the lower edges of the lining dimensioned to cover theend walls to effect a complete fluid and vapor impervious lining aboutthe insulated space.

The strips of fluid and vapor impervious material used to form themembrane should be of a material which is temperature-insensitive andwhich retains its strength and ductility and is not embrittled at thecold temperature of the liquid. For this purpose, use can be made offilm or sheet stock of from .006 to .030 inch formed of such metals asaluminum and alloys of aluminum, copper, brass, stainless steel or otheraustenitic steels or high nickel steels, or plastic film stock such asglass fiber reinforced polyester sheets, polyesters and the like.

Means are provided adjustably to suspend the lining from its upper edgeinto the insulated space to position the lining within the insulatedspace 20 with the walls of the lining adjacent the inner surfaces of thehousing walls but free therefrom to permit relative movement inexpansion and contraction.

To compensate for expansion and contraction in the horizontal direction,the panels can be formed with periodic laterally spaced apart verticallyextending corrugations (not shown) or else corrugated at their edgeswhere they are joined one to another but it is preferred to compensatefor such change in dimension by the formation of the panels with adimplcd construction 29 throughout or with a cross-ribbed checker-boardconstruction for making additional material available in all directionsin amounts to compensate 'for the expansion and contraction adapted totake place without substantial dimensional change.

The modification shown in FIG. 1 illustrates one means for suspensionand for compensating for contraction and expansion of the membrane inthe lengthwise direction. In this modification, the upper edge portionof each of the panels before or after joinder, are formed with aplurality of horizontally disposed, vertically spaced apart corrugations44 dimensioned to make an amount of material available calculated toexceed the amount of con traction otherwise taking place throughout thelength of the strips so that the bottom portion of the lining will beable to remain at rest at all times on the bottom wall of the supportinghousing. Beyond the corrugated portion, the upper edge of the panels isformed with means for fixing the position of the lining as by attachmentto the housing. By way of example, the upper edge is turned to anoutwardly extending flange 46 adapted to be engaged in the housing wallfor support and in a manner to suspend the remainder of the liningwithin the insulated space.

In another modification, shown in FIG. 3, the formed lining is suspendedwithin the insulated housing from a resilient means connected to the topwall of the tank. In the illustrated modification, the mounting meanscomprises angle irons 52 or other rigid structural members which arehorizontally disposed and attached to the upper edge portion of themembrane or lining about the insulated space. The structural membershave a plurality of spaced apart openings 53 through which elongate rods54 may extend. The upper end of each of the rod members is pivotallyconnected to the top wall of the housing as by means of an eye 56engaged upon a hook 58 of a bracket 59 rigid with a horizontallydisposed beam 60 fixed to the upper portion of the insulated space. Thethrough-extending end portion of each of the rods 54 is threaded, as at62, for enabling a washer 66 and a nut 64 threadably to be received onthe end thereof. A compression spring 68 is disposed between the washerand the structural member 52 in a manner resiliently to urge thesupporting structure 52 in the upward direction. By adjustment of thenut member on the rod, it becomes possible to raise or lower thestructural member 52 by an amount to compensate for the expansion andcontraction found to take place. Suflicient flexibility exists by reasonof the resilient support to take care of any additional contraction orexpansion which might take place. The force for deformation of thesprings is calculated to be less than the force required to rupture thelining. It is desirable, though not essential, to make use of anadditional element within the container for urging the membraneoutwardly into position of use and to prevent collapse upon removal ofliquid. For this purpose, use can be made of a spider construction ofthe type described in my previously issued Patent No. 2,954,892.

A further means, illustrated in FIGS. 1 and 2 of] the drawings,comprises light weight, horizontally disposed beams 70 fixed to theinner surfaces of the panels in vertically spaced apart relation toprovide relatively rigid,

structurally strong, horizontally disposed ledges in the side panels aswell as in the front and back panels. Extending crosswise betweenopposite ledges are one or more bowed strips 72 of wood or otherrelatively rigid resilient material which are efiective as spreader barsconstantly to urge the opposite ledges in the direction away from eachother and towards engagement with the insulating supporting wall. In theassembled relation, there will be spreader bars 72 extending crosswisebetween the opposite side walls and other spreader bars 74 extendinglengthwise between the front and back walls.

It will be apparent from the foregoing that I have provided a simplifiedmeans for the construction of a membrane enclosure for use in aninsulated storage tank which is adapted to house liquids, and especiallyextremely cold liquids like liquefied natural gas. The use of continuousstrips of membrane material to extend lengthwise over opposite walls andacross the bottom wall markedly simplifies the construction andmaterially improves its operation since the number of joints along theadjacent edges of the strips is materially reduced by comparison withthe preformed panel construction of the type heretofore employed.

It will be understood that changes may be made in the details ofconstruction, arrangement and operation without departing from thespirit of the invention, especially as defined in the following claims.

I claim:

1. In a membrane tank for liquid storage comprising a rigid housing ofstructural strength having vertically disposed walls, a bottom wall anda top wall defining a storage space therebetween, a thin collapsiblemembrane container of fluid and vapor impervious material supported fromthe upper edge portion for suspension within said storage space to linethe walls of said housing and against which the membrane rests inresponse to liquid load in storage while remaining free thereof forrelative movements responsive to expansion and contraction, theimprovement wherein the said membrane container comprises elongatestrips of said fluid and vapor impervious material extendingcontinuously across the bottom wall of the housing and up oppositevertical walls to a level above the liquid level and in which the stripsare arranged in side-by-side relation with the adjacent edges joined insealing relation to form a continuous panel dimensioned to have a widthcorresponding to the width ofi said vertical walls, and other elongatestrips extending continuously from the bottom wall to the level of theliquid in the container and arranged in side-by-side relationship withthe lateral edges joined in sealing relation to form other panelsdimensioned to have widths corresponding to the others of said verticalwalls, with the edges of one panel being joined with the edges ofadjacent panels in sealing relation to define the membrane containertherebetween and in which said strips are of dimpled constructionsubstantially throughout their area for expansion and contractionwithout dimensional change.

2. A membrane tank as claimed in claim 1 in which the membrane containeris formed of strips of temperature insensitive material which do notlose their strength and ductility at extremely low temperature.

3. A membrane tank as claimed in claim 1 in which the rigid housingcomprises an insulated housing formed of thermal insulating materialhaving structural strength and dimensional stability for support of themembrane container under load.

4. A membrane tank as claimed in claim 3 in which the thermal insulatingmaterial comprises panels of balsa wood.

5. A membrane tank as claimed in claim 1 in which the panels forming themembrane container have vertically disposed, laterally spaced apartcorrugations for enabling expansion and contraction in the crosswisedirection without dimensional change.

6. A membrane tank as claimed in claim 1 in which the panels of themembrane container are cross ribbed for expansion and contractionwithout dimensional change.

7. A membrane tank as claimed in claim 1 in which the panels of themembrane container are corrugated in the edge sections where the stripsare joined one to the other for expansion and contraction in thecross-wise direction without dimensional change.

8. A membrane tank as claimed in claim 1 which includes means in theupper end portion of the panels of the membrane container for enablingexpansion and contraction in the lengthwise direction withoutdimensional change.

9. A membrane tank as claimed in claim 8 in which the means permittingexpansion and contraction without dimensional change compriseshorizontally arranged vertically spaced apart corrugations.

10. A membrane tank as claimed in claim 8 in which the means in theupper end portion of the panels for enabling expansion and contractionwithout dimensional change comprises a frame fixed to the upper portionof the housing, hanger rods suspended from said frame and shiftablerelative thereto in the vertical direction, means securing the upper endportions of said panels to said hanger rods, and means resilientlyurging said rods towards a raised position.

.11. A membrane tank as claimed in claim 10 which includes means foradjusting said resilient means on said hanger rods to adjust theposition of the panels in the vertical direction.

12. A membrane tank as claimed in claim 1 which includes means withinthe housing constantly urging the vertically disposed panels of themembrane container in the direction towards the supporting wall of thehousing.

13. A membrane tank as claimed in claim 12 in which the means constantlyurging the panels outwardly in the direction of the supporting walls ofthe housing comprises horizontally disposed vertically spaced apartledges on the inner surfaces of the vertically disposed panels,resilient spreader bars dimensioned to have a length greater than thedistance between opposite Walls and bowed to extend between saidopposite walls with the ends bearing against said ledges.

References Cited in the file of this patent UNITED STATES PATENTS Re.6,157 Munzinger Dec. 1, 1874 537,119 Levey Apr. 9, 1895 1,748,575Maskrey Feb. 25, 1930 2,695,744 Gattuso Nov. 30, 1954 2,722,336 Wexleret a1. Nov. 1, 1955 2,963,873 Stowers Dec. 13, 1960

1. IN A MEMBRANE TANK FOR LIQUID STORAGE COMPRISING A RIGID HOUSING OFSTRUCTURAL STRENGTH HAVING VERTICALLY DISPOSED WALLS, A BOTTOM WALL ANDA TOP WALL DEFINING A STORAGE SPACE THEREBETWEEN, A THIN COLLAPSIBLEMEMBRANE CONTAINER OF FLUID AND VAPOR IMPERVIOUS MATERIAL SUPPORTED FROMTHE UPPER EDGE PORTION FOR SUSPENSION WITHIN SAID STORAGE SPACE TO LINETHE WALLS OF SAID HOUSING AND AGAINST WHICH THE MEMBRANE RESTS INRESPONSE TO LIQUID LOAD IN STORAGE WHILE REMAINING FREE THEREOF FORRELATIVE MOVEMENTS RESPONSIVE TO EXPANSION AND CONTRACTION, THEIMPROVEMENT WHEREIN THE SAID MEMBRANE CONTAINER COMPRISES ELONGATESTRIPS OF SAID FLUID AND VAPOR IMPERVIOUS MATERIAL EXTENDINGCONTINUOUSLY ACROSS THE BOTTOM WALL OF THE HOUSING AND UP OPPOSITEVERTICAL WALLS TO A LEVEL ABOVE THE LIQUID LEVEL AND IN WHICH THE STRIPSARE ARRANGED IN SIDE-BY-SIDE RELATION WITH THE ADJACENT EDGES JOINED INSEALING RELATION TO FORM A CONTINUOUS PANEL DIMENSIONED TO HAVE A WIDTHCORRESPONDING TO THE WIDTH OF SAID VERTICAL WALLS, AND OTHER ELONGATESTRIPS EXTENDING CONTINUOUSLY FROM THE BOTTOM WALL TO THE LEVEL OF THELIQUID IN THE CONTAINER AND ARRANGED IN SIDE-BY-SIDE RELATIONSHIP WITHTHE LATERAL EDGES JOINED IN SEALING RELATION TO FORM OTHER PANELSDIMENSIONED TO HAVE WIDTHS CORRESPONDING TO THE OTHERS OF SAID VERTICALWALLS, WITH THE EDGES OF ONE PANEL BEING JOINED WITH THE EDGES OFADJACENT PANELS IN SEALING RELATION TO DEFINE THE MEMBRANE CONTAINERTHEREBETWEEN AND IN WHICH SAID STRIPS ARE OF DIMPLED CONSTRUCTIONSUBSTANTIALLY THROUGHOUT THEIR AREA FOR EXPANSION AND CONTRACTIONWITHOUT DIMENSIONAL CHANGE.